Electric motor drive device

ABSTRACT

An electric motor drive device controls driving of a motor having open windings of two or more phases having end points that are open to each other. The switching arbitrator determines switching between a single-sided and dual-sided drive mode and arbitrates output of each of the inverters at a time of switching wherein output of the motor is continuous before and after the drive mode switching. The single-sided drive mode is a mode in which one of the two inverters performs switching drive. The dual-sided drive mode in which both the two inverters perform switching drive. The switching arbitrator gradually changes and increases the power level of the drive-start-side inverter from zero when the single-sided drive mode is switched to the dual-sided drive mode, and gradually changes and decreases the power level of the drive-end-side inverter to zero when the dual-sided drive mode is switched to the single-sided drive mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the U.S. bypass application of InternationalApplication No. PCT/JP2020/005863 filed on Feb. 14, 2020 whichdesignated the U.S. and claims priority to Japanese Patent ApplicationNo. 2019-027470, filed on Feb. 19, 2019, and Japanese Patent ApplicationNo. 2020-018720, filed on Feb. 6, 2020, the contents of all of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an electric motor drive device.

BACKGROUND

Conventionally, there has been known a technique for driving a single ACmotor provided between two inverters. For example, the inverter systemdisclosed in U.S. Pat. No. 8,102,142B2 uses a combination of two powersources of different types (for example, an output type power source anda capacitive type power source), and drives a motor with the moresuitable power source depending on the operating temperature range. Thesystem takes into consideration the state and characteristics of eachpower source and switches between one-side power drive and two-sidepower drive to compensate for an instantaneous drop in the output of themotor.

SUMMARY

An electric motor drive device according to a first aspect of thedisclosure controls the driving of a motor including two or more phasesof open windings of which end points are open to each other, using twoinverters individually connected to two power sources. Such an electricmotor drive device includes a first inverter, a second inverter, and acontrol unit.

The first inverter receives DC power from a first power source, includesa plurality of first switching elements so disposed as to correspond tothe phases of the open windings, and is connected to one ends of theopen windings. The second inverter receives DC power from a second powersource, includes a plurality of second switching elements so disposed asto correspond to the phases of the open windings, and is connected tothe other ends of the open windings.

The control unit includes two inverter control circuits of a firstinverter control circuit that generates a first voltage and a secondinverter control circuit that generates a second voltage command, basedon a torque command, and a switching arbitrator. The first voltagecommand is an output voltage command to the first inverter. The secondvoltage command is an output voltage command to the second inverter. Theswitching arbitrator determines the switching between a single-sideddrive mode and a dual-sided drive mode and arbitrates output of each ofthe inverters at a time of switching so that output of the motor iscontinuous before and after the drive mode switching. The single-sideddrive mode is a mode in which one of the two inverters performsswitching drive. The dual-sided drive mode is a mode in which both thetwo inverters perform switching drive.

At least one of the inverter control circuits has a function ofadjusting the level of the power supplied from the two power sources tothe two inverters. The switching arbitrator gradually changes andincreases the power level of the drive-start-side inverter from zerowhen the single-sided drive mode is switched to the dual-sided drivemode. When the dual-sided drive mode is switched to the single-sideddrive mode, the switching arbitrator gradually changes and decreases thelevel of power of the drive-end-side inverter to zero.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features of the present disclosure will be made clearer by thefollowing detailed description, given referring to the appendeddrawings. In the accompanying drawings:

FIG. 1 is a diagram of the overall configuration of a system to which anelectric motor drive device of the first embodiment is applied;

FIG. 2A is a diagram illustrating switching drive in a single-sideddrive mode;

FIG. 2B is a diagram illustrating switching drive in a dual-sided drivemode;

FIG. 3A is an N-T characteristic diagram illustrating the region inwhich the single-sided drive mode is applied;

FIG. 3B is an N-T characteristic diagram illustrating the region inwhich the dual-sided drive mode is applied;

FIG. 4 is a schematic configuration diagram of a control unit of thefirst embodiment;

FIG. 5A is a diagram for explaining fluctuation in the voltage across MGcoil ends at the time of switching between the single-sided drive modeand the dual-sided drive mode;

FIG. 5B is a schematic control configuration diagram of the time ofswitching between the single-sided drive mode and the dual-sided drivemode;

FIG. 6 is a flowchart of a drive mode switching process according to thefirst embodiment;

FIG. 7 is a control block diagram for executing the drive mode switchingprocess (instantaneous correction of voltage command and gradual changein power level) according to the first embodiment;

FIG. 8 is a sub-flowchart illustrating a specific example of theswitching determination in FIG. 6 ;

FIG. 9 is a time chart illustrating drive mode switching operationaccording to a comparative example;

FIG. 10 is a time chart illustrating drive mode switching operationaccording to the first embodiment;

FIG. 11 is a diagram for explaining gradual change in power distributioncorresponding to an enlarged view of the XI portion in FIG. 10 ;

FIG. 12A is a diagram illustrating switching determination by a voltageutilization factor used for MG control;

FIG. 12B is a diagram illustrating switching determination by aself-inverter voltage utilization factor;

FIG. 13 is a time chart illustrating the operation in a slow changeprocess according to a second embodiment;

FIG. 14A is a diagram for explaining fluctuation in the voltage acrossMG coil ends at the time of switchover from a first invertersingle-sided drive to a second inverter single-sided drive mode;

FIG. 14B is a schematic control configuration diagram at the time ofswitchover from first inverter single-sided drive to second invertersingle-sided drive;

FIG. 15A is a control block diagram for executing a drive mode switchingprocess according to a third embodiment;

FIG. 15B is a control block diagram for executing the drive modeswitching process according to the third embodiment;

FIG. 16 is a flowchart of the drive mode switching process according tothe third embodiment;

FIG. 17 is a time chart illustrating the switching operation accordingto the third embodiment when the voltages of two power sources areequal;

FIG. 18 is a time chart illustrating switching operation according tothe third embodiment when the voltages of two power sources aredifferent;

FIG. 19 is a diagram of the overall configuration of a system to whichthe electric motor drive device of a fourth embodiment is applied;

FIG. 20A is a diagram illustrating switching drive in a star connectioncircuit in a single-sided drive mode;

FIG. 20B is a diagram illustrating switching drive in an H-bridgecircuit in a dual-sided drive mode;

FIG. 21 is a time chart illustrating drive mode switching operationaccording to the fourth embodiment;

FIG. 22 is a diagram of the overall configuration of a system to whichthe electric motor drive device of a fifth embodiment is applied;

FIG. 23 is a diagram of the overall configuration of a system to whichthe electric motor drive device of a sixth embodiment is applied; and

FIG. 24 is a time chart illustrating drive mode switching operationaccording to the sixth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

U.S. Pat. No. 8,102,142B2 describes the switching of a drive patternusing one or both of two power sources having different characteristicsbased on the driving state of the apparatus and the output of the motor.However, as an unavoidable problem of a two-power source, two-invertersystem, the voltage across the two ends of the motor coil alwayssuddenly changes when the drive mode is switched. U.S. Pat. No.8,102,142B2 does not mention a specific switching method that couldaddress this problem.

The two inverters each independently output voltage pulses, and thevoltage to be applied to the motor coil is determined by the voltagepulses. In other words, unless each inverter output is controlled to anoptimum value required by the motor at that point in time, torquefluctuation occurs because of current disturbance caused by excessive orinsufficient voltage. In the worst case, overcurrent generated byexcessive voltage application may cause component failure. This problemapplies not only to a two-power source, two-inverter system, but also toa system in which two inverters are connected to one common powersource.

An object of the disclosure is to provide an electric motor drive devicehaving a two-inverter configuration that stabilizes and maintaincontinuity of motor output at the time of switching between asingle-sided drive mode and a dual-sided drive mode.

An electric motor drive device according to a first aspect of thedisclosure controls the driving of a motor including two or more phasesof open windings of which end points are open to each other, using twoinverters individually connected to two power sources. Such an electricmotor drive device includes a first inverter, a second inverter, and acontrol unit.

The first inverter receives DC power from a first power source, includesa plurality of first switching elements so disposed as to correspond tothe phases of the open windings, and is connected to one ends of theopen windings. The second inverter receives DC power from a second powersource, includes a plurality of second switching elements so disposed asto correspond to the phases of the open windings, and is connected tothe other ends of the open windings.

The control unit includes two inverter control circuits of a firstinverter control circuit that generates a first voltage and a secondinverter control circuit that generates a second voltage command, basedon a torque command, and a switching arbitrator. The first voltagecommand is an output voltage command to the first inverter. The secondvoltage command is an output voltage command to the second inverter. Theswitching arbitrator determines the switching between a single-sideddrive mode and a dual-sided drive mode and arbitrates output of each ofthe inverters at a time of switching so that output of the motor iscontinuous before and after the drive mode switching. The single-sideddrive mode is a mode in which one of the two inverters performsswitching drive. The dual-sided drive mode is a mode in which both thetwo inverters perform switching drive.

At least one of the inverter control circuits has a function ofadjusting the level of the power supplied from the two power sources tothe two inverters. The switching arbitrator gradually changes andincreases the power level of the drive-start-side inverter from zerowhen the single-sided drive mode is switched to the dual-sided drivemode. When the dual-sided drive mode is switched to the single-sideddrive mode, the switching arbitrator gradually changes and decreases thelevel of power of the drive-end-side inverter to zero.

Here, the term drive-start-side inverter refers to an inverter thatstarts switching drive from the current idle state. The drive-end-sideinverter is an inverter that terminates the switching drive that hasbeen performed and shifts to an idle state. The term zero of the powerlevel is not limited to the 0 W in a strict sense, but includes a smallvalue within a range determined to be near zero based on the commonknowledge in the relevant technical field. The term gradual changerefers to a level of rate change that feedback control can follow.

The switching arbitrator of the disclosure makes the output of the motorcontinuous before and after the switching by gradually changing thepower level of each inverter at the time of the drive mode switching.Consequently, it is possible to avoid damage of the apparatus caused bytorque fluctuation of the motor or overcurrent generated during thefluctuation. The torque of the motor can be prevented from fluctuatingdue to the influence of the power fluctuation caused by the operation atthe time of the drive mode switching.

An electric motor drive device according to a second aspect of thedisclosure controls, by using two inverters individually connected totwo power sources, driving of a motor including a first winding set anda second winding set of three or more phases connected by a starconnection or a delta connection. Such an electric motor drive deviceincludes a first inverter, a second inverter, and a control unit.

The first inverter includes multiple first switching elements thatreceive DC power from the first power source and are disposed tocorrespond to the phases of the first winding set, and is connected tothe second winding set. The second inverter includes multiple secondswitching elements that receive DC power from the second power sourceand are disposed to correspond to the phases of the second winding set,and is connected to the first winding set. The configuration of thecontrol unit is the same as that of the electric motor drive device ofthe first aspect.

An electric motor drive device according to a third aspect of thedisclosure controls the driving of a motor including two or more phasesof open windings of which end points are open to each other, using twoinverters individually connected to a common power source. The electricmotor drive device includes a first inverter, a second inverter, acommon high-potential-side wiring, a common low-potential side wiring, aswitch, and a control unit.

The first inverter includes a plurality of first switching elements sodisposed as to correspond to the phases of the open windings, and isconnected to one ends of the open windings. The second inverter includesa plurality of second switching elements so disposed as to correspond tothe phases of the open windings, and is connected to the other ends ofthe open windings. The common high-potential-side wiring connectshigh-potential-side wirings of the first and second inverters. Thecommon low-potential-side wiring connects low-potential-side wirings ofthe first and second inverters. The switch is disposed on at least oneof the common high-potential-side wiring and the commonlow-potential-side wiring and is capable of interrupting off a currentpath.

An electric motor drive device according to the third aspect is capableof operating the other inverter in the single-sided drive mode in a starconnection circuit formed by neutral point coupling of the one inverterin an open state of the switch. With an H-bridge circuit including thefirst switching element and the second switching element of therespective corresponding phases with the switch closed, operation ispossible in the dual-sided drive mode. In the control unit, at least oneinverter control circuit has a function of adjusting the level of thepower supplied from the common power source to the two inverters. Otherconfigurations of the control unit are the same as that of the electricmotor drive device of the first aspect.

An electric motor drive device according to a fourth aspect of thedisclosure controls, by using two inverters connected to a common powersource, driving of a motor including a first winding set and a secondwinding set of three or more phases connected by a star connection or adelta connection. The motor is, for example, a six-phase dual motorincluding two sets of three-phase windings. The electric motor drivedevice includes a first inverter, a second inverter, a commonhigh-potential-side wiring, a common low-potential side wiring, and acontrol unit.

The first inverter includes a plurality of first switching elementsdisposed in correspondence to the respective phases of the first windingset, and is connected to the first winding set. The second inverterincludes a plurality of second switching elements disposed incorrespondence to the respective phases of the second winding set, andis connected to the second winding set. The configuration of the commonhigh-potential-side wiring, the common low-potential side wiring, andthe control unit is the same as that of the electric motor drive deviceof the third aspect.

Embodiments of an electric motor drive device will now be described withreference to the drawings. The first to sixth embodiments arecollectively referred to as the present embodiment. The electric motordrive device according to the present embodiment is a device thatcontrols the driving of a motor generator (MG), which is a three-phaseAC motor, in a system in which two inverters drive the MG, which is apower source of a hybrid or electric vehicle. The terms MG and MGcontrol device in the embodiment respectively correspond to the termsmotor and electric motor drive device.

The first, fourth, fifth, and sixth embodiments combine differentnumbers of power sources in the system to which the MG control device isapplied and different winding configurations of the MG. As for thenumber of power sources, two power sources or one common power source isused. As for the winding configuration of the MG, open windings in whichend points are uncoupled, i.e., are open, or two winding sets that arestar-connected and delta-connected are used. The first embodiment isapplied to a two-power source, open winding system, and the fourthembodiment is applied to a one-power source, open winding system. Thefifth embodiment is applied to a two-power sources, two-open winding setsystem, and the sixth embodiment is applied to a one-power source,two-open winding set system.

The second and third embodiments have the same system configuration asthat of the first embodiment except that the drive mode switchingcontrol differs. The switching control of the second and thirdembodiments can also be used in the system configurations of the fourthto sixth embodiments. Mainly the first to third embodiments will bedescribed in detail below. For the fourth to sixth embodiments, thetechnical concepts of the first to third embodiments are applied as theyare or with some modifications.

[System Configuration of First Embodiment]

FIG. 1 illustrates the overall configuration of a two-power source,two-inverter system of the first embodiment i.e., a system that uses twopower sources 11 and 12 and two inverters 60 and 70. The systemconfiguration in FIG. 1 is also applied to the second and thirdembodiments. An MG 80 is a permanent magnet synchronous type 3-phase ACmotor including a U-phase winding 81, a V-phase winding 82, and aW-phase winding 83. When the system is applied to a hybrid vehicle, theMG 80 has a function as a motor that generates torque for driving thedrive wheels, and a function as a generator that can generateelectricity by being driven by the kinetic energy of the vehicletransmitted from the engine and the drive wheels.

In the MG 80 of the first embodiment, the three-phase windings 81, 82,and 83 have an open winding configuration in which the end points arenot coupled to each other. The output terminals of the respective phasesof the first inverter 60 are connected to one ends 811, 821, and 831 ofthe three-phase open windings 81, 82, and 83, and the output terminalsof the respective phases of the second inverter 70 are connected to theother ends 812, 822, and 832 of the three-phase open windings 81, 82,and 83. A rotation angle sensor 85 includes a resolver, and detects amachine angle θm of the MG 80. The machine angle θm is converted to anelectrical angle θe by an electrical angle calculator 87 of a controlunit 300.

The first power source 11 and the second power source 12 are twoindependent power sources insulated from each other, and each of them isa chargeable/dischargeable electrical storage device, e.g., a secondarybattery such as nickel hydrogen, lithium ion, or the like, an electricdouble layer capacitor, or the like. For example, an output typelithium-ion battery may be used as the first power source 11, and acapacity type lithium-ion battery may be used as the second power source12. The power of the power sources 11 and 12 is represented by state ofcharge (SOC).

The two inverters 60 and 70 individually receive input of DC power fromthe two power sources 11 and 12. The first power source 11 can exchangepower with the MG 80 via the first inverter 60, and the second powersource 12 can exchange power with the MG 80 via the second inverter 70.The output of the first inverter 60 is equal to the power of the firstpower source 11, and the output of the second inverter 70 is equal tothe power of the second power source 12. The current flowing from thefirst power source 11 to the first inverter 60 is referred to as a firstpower source current Ib1, and the current flowing from the second powersource 12 to the second inverter 70 is referred to as a second powersource current Ib2.

The MG 80 receives power from the first power source 11 via the firstinverter 60, and receives power from the second power source 12 via thesecond inverter 70. A U-phase voltage VU1, a V-phase voltage VV1, and aW-phase voltage VW1 are applied to the three-phase open windings 81, 82,and 83 from the first inverter 60 side. A U-phase voltage VU2, a V-phasevoltage VV2, and a W-phase voltage VW2 are applied to the three-phaseopen windings 81, 82, and 83 from the second inverter 70 side.

A current sensor 84 for detecting the phase currents applied to thethree-phase open windings 81, 82, and 83 is disposed, for example, inthe power path from the first inverter 60 to the MG 80. In the exampleof FIG. 1 , a V-phase current Iv and a W-phase current Iw are detected,but any two-phase or three-phase current may be detected. The currentsensor 84 may be disposed in the power path from the second inverter 70to the MG 80, or in paths of both the first inverter 60 and the secondinverter 70.

A first capacitor 16 is connected between a high-potential-side wiringP1 and a low-potential-side wiring N1, and a second capacitor 17 isconnected between a high-potential-side wiring P2 and alow-potential-side wiring N2. A first voltage sensor 18 detects a firstpower source voltage VH1 input from the first power source 11 to thefirst inverter 60. A second voltage sensor 19 detects a second powersource voltage VH2 input from the second power source 12 to the secondinverter 70. The first power source voltage VH1 and the second powersource voltage VH2 may be equal or different. A shared power P_INV1 ofthe first inverter 60 is represented by P_INV1=Ib1×VH1, and a sharedpower P_INV2 of the second inverter 70 is represented by P_INV2=Ib2×VH2.The power sum P_INV1+P_INV2 of the two inverters 60 and 70 is input tothe MG 80.

An MG control device 101 includes the first inverter 60, the secondinverter 70, the control unit 300, and drive circuits 67 and 77. Thefirst inverter 60 is so provided as to correspond to the respectivephases of the open windings 81, 82, and 83, and includes sixbridge-connected first switching elements 61 to 66. The switchingelements 61, 62, and 63 are upper-arm switching elements of the U-phase,the V-phase, and the W-phase, respectively, and the switching elements64, 65, and 66 are lower-arm switching elements of the U-phase, theV-phase, and the W-phase, respectively. The second inverter 70 is soprovided as to correspond to the respective phases of the open windings81, 82, and 83, and includes six bridge-connected second switchingelements 71 to 76. The switching elements 71, 72, and 73 are upper-armswitching elements of the U-phase, the V-phase, and the W-phase,respectively, and the switching elements 74, 75, and 76 are lower-armswitching elements of the U-phase, the V-phase, and the W-phase,respectively.

The respective switching elements 61 to 66 and 71 to 76 are implementedby, for example, IGBTs, and are connected in parallel with flywheeldiodes that permit current to flow from the low-potential side to thehigh-potential-side. To prevent short-circuiting between thehigh-potential-side wirings P1 and P2 and the low-potential-side wiringsN1 and N2, the upper arm elements and the lower arm elements of therespective phases are controlled so that they are not simultaneouslyturned on and are turned on and off complementarily, that is, one isturned on when the other is turned off.

The control unit 300 is implemented by a microcomputer or the like, andincludes a CPU, a ROM, an I/O and a bus line connecting these components(not illustrated). The control unit 300 executes control by softwareprocessing by executing, by a CPU, a program previously stored in atangible memory device (that is, a readable non-temporary tangiblerecording medium), such as a ROM, and hardware processing by a dedicatedelectronic circuit.

The control unit 300 includes a first inverter control circuit 301 thatgenerates a first voltage command or output voltage command to the firstinverter 60, and a second inverter control circuit 302 that generates asecond voltage command or output voltage command to the second inverter,based on information of a torque command trq* and a detected value.Information such as an electrical angle θe and power source voltages VH1and VH2 is input to the respective inverter control circuits 301 and302. The first drive circuit 67 outputs, to the first inverter 60, agate signal based on the first voltage command generated by the firstinverter control circuit 301. The second drive circuit 77 outputs, tothe second inverter 70, a gate signal based on the second voltagecommand generated by the second inverter control circuit 302.

Temperature sensors 861, 862, 863, 864, and 865 respectively detect thetemperature Hb1 of the first power source 11, the temperature Hb2 of thesecond power source 12, the temperature Hinv1 of the first inverter 60,the temperature Hinv2 of the second inverter 70, and the temperature Hmgof the MG 80, and reports the temperatures to the control unit 300. Thetemperatures of the respective components are one of the determinationfactors in the drive mode switching determination described below.

[Overview of Single-Sided Drive Mode and Dual-Sided Drive Mode]

The control mode in which one of the two inverters 60 and 70 performsswitching drive is referred to as a single-sided drive mode, and acontrol mode in which both inverters 60 and 70 perform switching drivereferred to as a dual-sided drive mode. The present embodiment focuseson the operation of switching between the single-sided drive mode andthe dual-sided drive mode. As an example of switchover from thesingle-sided drive mode to the dual-sided drive mode, switchover fromthe single-sided drive mode by the first inverter 60 to the dual-sideddrive mode will now be mainly described. Since the switchover from thesingle-sided drive mode by the second inverter 70 to the dual-sideddrive mode is also similar, description thereof is omitted but does notlimit the functional means.

FIG. 2A illustrates switching drive in the single-sided drive mode, andFIG. 2B illustrates switching drive in the dual-sided drive mode. In thesingle-sided drive mode, only the first inverter 60 performs switchingdrive. In the second inverter 70, one of the upper-arm switchingelements 71, 72, and 73 and the lower-arm switching elements 74, 75, and76 of the respective phases are turned on and the other is turned off toelectrically establish neutral point coupling. In the dual-sided drivemode, both inverters 60 and 70 perform switching drive to serialize thevoltages of the two power sources 11 and 12.

The N-T characteristic diagrams of FIGS. 3A and 3B are referred to forillustrating the concept of drive mode switching. The hatched area ineach drawing is a preferred area to which the drive mode is applied. Thesingle-sided drive mode illustrated in FIG. 3A is advantageous under lowload because it has the advantage of high efficiency under low load andthe disadvantage of a low upper limit for high load performance. Thedual-sided drive mode illustrated in FIG. 3B is advantageous under highload because it has the advantage of a high upper limit for high loadperformance and the disadvantage of low efficiency under low load.

Therefore, driving in which output and efficiency are compatible can beachieved by maintaining sufficient output in the dual-sided drive modeunder high load and switching over to the single-sided drive mode underlow load to achieve low loss drive.

[Problems and Focus Points]

As an unavoidable problem of the two-power source, two-inverter system,the voltage across the two ends of the MG always suddenly changes whenthe drive mode is switched. That is, the two inverters 60 and 70 eachindependently output voltage pulses, and the voltage to be applied tothe MG coils is determined by the voltage pulses. In other words, unlessthe outputs of the respective inverters 60 and 70 are controlled tooptimum values required by the MG 80 at that point in time, torquefluctuation occurs because of current disturbance caused by excessive orinsufficient voltage. In the worst case, overcurrent generated byexcessive voltage application may cause component failure.

Therefore, an object of the first embodiment is to stabilize the MGoutput before and after the drive mode switching and to maintaincontinuity in accordance with the principle that desired MG output andinverter outputs can be obtained by independently and concertedlycontrolling the outputs of the respective inverters 60 and 70. Morespecifically, the following three points should be taken intoconsideration.

[1] Gradually change the outputs of the inverters at the rising andfalling edges when the drive mode is switched to avoid sharp change inthe outputs.

[2] Eliminate output fluctuation through instantaneous correction of avoltage command for the purpose of eliminating the cause of outputchange of a self-inverter within the self-inverter.

[3] Achieve both high output drive and low loss drive at low output bystable switching at the timing of target MG output by appropriately anduniquely determining the switching without depending on a state changebefore and after the switching.

[Configuration of Control Unit]

FIG. 4 illustrates the schematic configuration of the control unit 300.In the following drawings, the inverter is referred to as INV. The firstinverter control circuit 301 and the second inverter control circuit 302respectively drive the first inverter 60 and the second inverter 70 bydq control (i.e., vector control in dq axis coordinates). The invertercontrol circuits 301 and 302 may be disposed in separate microcomputers,or may be disposed in one common microcomputer. The respective invertercontrol circuits 301 and 302 generate independent and concerted voltagecommands for the system to work as a two-power source, two-invertersystem.

Since the MG 80 is shared, the detected values of the angle(specifically, the electrical angle θe) and the three-phase current maybe shared as information obtained by the control unit 300. However, asindicated by the dashed lines, multiple current sensors 84 and rotationangle sensors 85 may be provided, and the inverter control circuits 301and 302 may obtain the corresponding detected values. When feedforwardcontrol is performed, the second inverter control circuit 302 may notacquire the detected values of the three-phase current as indicated bythe dashed lines.

At least one of the inverter control circuits of the control unit 300has a function of adjusting the level of power supplied from the twopower sources 11 and 12 to the two inverters 60 and 70. In theconfiguration illustrated of FIG. 4 , the first inverter controlcircuits 301 serves as a torque management circuit and provides torquethrough feedback control. The second inverter control circuit 302 servesas a power management circuit and manages the power through feedforwardcontrol and power distribution control.

The power management circuit has a function of adjusting the level ofpower supplied from the two power sources 11 and 12 to the two inverters60 and 70. The power distribution control manages the distribution ofpower supplied from the two power sources 11 and 12 to the two inverters60 and 70. In the following drawings, feedback is denoted as FB andfeedforward is denoted as FF. Note that the roles of the first invertercontrol circuit 301 and the second inverter control circuit 302 may beswitched.

In this configuration, while the first inverter control circuit 301performs feedback control to correct the disturbance suppression so thatthe torque follows the command, the second inverter control circuit 302performs feedforward control uniquely determined by the command tomanage the power of the respective inverters 60 and 70. Since, in thisway, the power management circuit adjusts the inverter power while thetorque management circuit performs feedback control to correct thedisturbance suppression, the control unit 300 achieves both the desiredMG torque and the desired power source power without any controlinterference.

However, since the inverter control circuits 301 and 302 independentlyperform dq control to drive the respective inverters 60 and 70, the MGtorque (output) and the inverter power readily fluctuate unless thevoltage across the MG coil ends generated by concerted inverter commandsare optimal for the MG 80. Such fluctuation becomes more significant inthe scene of switching between the single-sided drive mode and thedual-sided drive mode in which the voltage across the MG coil endschanges the most in a short time.

Therefore, the control unit 300 of the present embodiment includes aswitching arbitrator 303 that determines the switching between thesingle-sided drive mode and the dual-sided drive mode after therespective inverter control circuits 301 and 302 are sets to assume theroles of torque management and power management, and arbitrates theoutputs of the respective inverters 60 and 70 at the time of switching.The switching arbitrator 303 arbitrates change in the power level so asnot to be affected by change in the voltage across the MG coil ends atthe time of switching between the single-sided drive mode and thedual-sided drive mode, and makes the MG output before and after theswitching continuous.

In the configuration of FIG. 4 , the torque commands trq* and the powerdistribution requests from external higher-order control circuits areonce input to the switching arbitrator 303, and then reported to therespective inverter control circuits 301 and 302. However, alternativeto such a configuration, the torque commands trq* and the powerdistribution requests from external devices may be input to therespective inverter control circuits 301 and 302 and then reported tothe switching arbitrator 303.

The switching arbitrator 303 gradually changes and increases the powerlevel of the drive-start-side inverter from zero at the time ofswitchover from the single-sided drive mode to the dual-sided drivemode. At the time of switchover from the dual-sided drive mode to thesingle-sided drive mode, the switching arbitrator 303 gradually changesand decreases the power level of the drive-end-side inverter to zero. Apower level of zero is not limited to 0 W in a strict sense, butincludes a small value within a range determined to be near zero basedon the common knowledge in the relevant technical field. Consequently,the continuity of the MG output can be maintained and the controlfluctuation can be eliminated without depending on change in voltageacross the MG coil ends.

Here, the term drive-start-side inverter refers to an inverter that hasbeen in an idle state and start switching drive. The term drive-end-sideinverter refers to an inverter that ends the switching drive that hasbeen performed and shifts to an idle state. When the first invertersingle-sided drive mode switches over to the dual-sided drive mode, thesecond inverter 70 corresponds to the drive-start-side inverter. Whenthe dual-sided drive mode switches over to the first invertersingle-sided drive mode, the second inverter 70 corresponds to thedrive-end-side inverter.

The specific operation of drive mode switching will now be described foreach embodiment. The first and second embodiments describe the operationof shifting from the first inverter single-sided drive mode to thedual-sided drive mode or from the dual-sided drive mode to the firstinverter single-sided drive mode. The third embodiment describes theoperation of shifting from the first inverter single-sided drive mode tothe second inverter single-sided drive mode through the dual-sided drivemode.

First Embodiment

A control configuration according to the first embodiment relating tothe switching between the first inverter single-sided drive mode and thedual-sided drive mode will be described with reference to FIGS. 5A to12B. As illustrated in FIG. 5A, the amplitude of the voltage across theMG coil ends in the single-sided drive mode is voltage amplitudecorresponding to one power source, and in the dual-sided drive mode isvoltage amplitude corresponding to two power sources. Therefore, thevoltage across the MG coil ends always changes before and after theswitching between the single-sided drive mode and the dual-sided drivemode. This is an unavoidable problem for a two-power, two-invertersystem. If the system cannot respond to such change in the voltageacross ends of the MG coil, which is directly connected to thegeneration of three-phase current, excessive or insufficient voltagerequired for causing desired current to flow is generated across the MGcoil ends, and current disturbance will readily occur due to therelationship between the electric circuits and the pulse voltageoutputs.

FIG. 5B illustrates a schematic control configuration of the switchingbetween the first inverter single-sided drive mode and the dual-sideddrive mode. The basic control configuration in FIG. 5B includingcalculation of a current command Idq, calculation of a voltage commandVdq, and PWM control is a well-known technique and thus a descriptionthereof will be omitted. Hereinafter, a d-axis current command Id and aq-axis current command Iq are collectively referred to as a currentcommand Idq, and a d-axis voltage command Vd and a q-axis voltagecommand Vq are collectively referred to as a voltage command Vdq. Here,the d-axis voltage command Vd is zero or a negative value, and thephrase Vdq increases/decreases means that the absolute values of thed-axis voltage command Vd and the q-axis voltage command Vqincrease/decrease.

During switching drive by only the first inverter 60, the first powersource voltage VH1 is applied as an input voltage for PWM control.During switching drive of the both inverters 60 and 70 in which theswitching drive of the second inverter 70 is started while the switchingdrive of the first inverter 60 continues, a voltage sum (VH1+VH2) of thetwo power sources is applied as an input voltage for PWM control. Inthis way, switching occurs in the control from an MG viewpoint. If, atthe time of drive mode switching, synchronized switching of therespective inverters 60 and 70 cannot be performed, and applied voltageexcessive or insufficient relative to the required voltage is generated,current disturbance occurs.

In the first embodiment, the following switching process is executed toavoid the occurrence of excess or deficiency in the applied voltage andmaintain the continuity of the MG output. The drive mode switchingprocess according to the first embodiment will now be described withreference to the flowchart of FIG. 6 and the control block diagram ofFIG. 7 . In the description of the flowchart below, the symbol S denotesa step. In FIG. 7 , it is assumed that the first inverter controlcircuit 301 is the torque management circuit, and the second invertercontrol circuit 302 is the power management circuit.

In S10, the switching arbitrator 303 performs switching determination inaccordance with an output request to the MG 80, the SOC state of thepower sources 11 and 12, or the temperature of the power sources 11 and12, the inverters 60 and 70, or the MG 80. A specific example of theswitching determination will be described below with reference to FIG. 8. In S21, a voltage recognition value is set. The voltage recognitionvalue is determined by the power source voltages VH1 and VH2 of therespective inverters in the single-sided drive mode, and determined bythe voltage sum (VH1+VH2) of the two power sources in the dual-sideddrive mode.

In S22, the voltage command Vdq is instantaneously corrected at the timeof drive mode switching. At the time of switchover from the firstinverter single-sided drive mode to the dual-sided drive mode, thevoltage command Vdq1 is instantaneously corrected by expression (1.1).At the time of switchover from the dual-sided drive mode to the firstinverter single-sided drive mode, the voltage command Vdq1 isinstantaneously corrected by expression (1.2).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 1} \right\rbrack & \; \\{\left. {Vdq}\longrightarrow{Vdq} \right. \times \frac{{{VH}\; 1} + {{VH}\; 2}}{{VH}\; 1}} & (1.1) \\{\left. {Vdq}\longrightarrow{Vdq} \right. \times \frac{{VH}\; 1}{{{VH}\; 1} + {{VH}\; 2}}} & (1.2)\end{matrix}$

A supplementary description of the technical significance ofinstantaneous correction is provided. As it is well known, feedbackcontrol is follow-up control of a primary delay system. Since the MG 80includes coils, it is a primary delay system as an electric circuit.Therefore, it is clear that the response of the MG control forcontrolling the MG 80 of the primary delay system by the control of theprimary delay system is a primary delay. Therefore, the response tosharp change in the MG coil end voltage, i.e., stepwise change due toinstantaneous superposition of the output pulse voltages of bothinverters 60 and 70, such as in the case of the two-power source,two-inverter configuration, is always a first order delay. Accordingly,in the first embodiment, such problem is solved by instantaneouslycorrecting the voltage command Vdq. In the following second embodiment,the problem is solved by performing a slow change process.

In S23, since the inverter output and consequently the MG outputcontinue to maintain continuity, the voltage command Vdq1 is set as theamount to be transferred to the next control process. In the firstinverter control circuit 301, which is the torque management circuit, anintegral term of the feedback control is reset. In the second invertercontrol circuit 302, which is the power management circuit, a voltagecommand Vdq2 is set for power calculation in feedforward control. InS24, the power level of the output from the second inverter controlcircuit 302 for power management is gradually changed so as not to causedisturbance to the first inverter control circuit 301 for torquemanagement.

Supplementary description will be provided for the above-describedswitching process with reference to the block diagram of FIG. 7 . In theinstantaneous correction block of the first inverter control circuit301, the voltage command Vdq1 is instantaneously corrected in accordancewith the voltage recognition value only at the time of switching. In theintegral term resetting block, the amount to be transferred to the nextfeedback control is matched only at the time of switching. Consequently,a duty ratio INV1 duty commanded by the first inverter 60 is outputtedwhile maintaining continuity with that before and after switching.

In the power distribution control block of the second inverter controlcircuit 302, the voltage command Vdq2 is gradually changed and increasedfrom zero at a changing rate that can be flowed by the feedback controlof the first inverter control circuit 301. Consequently, a duty ratioINV2 duty in which the sharp change during switching is suppressed iscommanded to the second inverter 70.

Supplementary description will be provided on the details of thedetermination of switchover from the single-sided drive mode to thedual-sided drive mode in S10 of FIG. 6 with reference to thesub-flowchart of FIG. 8 . In S11, the MG control device 101 is driven inthe first inverter single-sided drive mode. In S12, it is determinedwhether the temperature Hb1 of the first power source 11 is higher thanthe upper limit of the appropriate range. In S13, it is determinedwhether the SOC of the first power source 11 is lower than the lowerlimit of the appropriate range. If YES in S12 or S13, it is preferableto reduce the load on the first power source 11 regardless of a highoutput request. Then, the process proceeds to S16, and the switchingarbitrator 303 determines to switchover from the first invertersingle-sided drive mode to the dual-sided drive mode.

In the dual-sided drive mode of S16, it is preferable that a pattern inwhich the inverters 60 and 70 are both driven in the PWM control mode isselected, and that the power is actively adjusted so that thetemperature and the SOC of the first power source 11 fall withinappropriate ranges. Note that the output may be limited depending on thetemperature of the first power source 11.

If NO in S12 and S13, it is determined in S14 whether there is a highoutput request to the MG 80. If YES in S14, it is further determined inS15 whether there is a request for high efficiency operation. If YES inS15, the process proceeds to S17, and the switching arbitrator 303determines to switchover from the first inverter single-sided drive modeto the dual-sided drive mode. In the dual-sided drive mode of S17, highefficiency operation is executed by selecting a pattern in which theinverter on the high-power level side is driven in a rectangular wavecontrol mode and the other inverter is driven in a PWM control mode.

If YES in S14 and NO in S15, the process proceeds to S16, and theinverters 60 and 70 are both driven in the PWM control mode in thedual-sided drive mode. In such a case, normal operation which is notintentional efficient operation is performed in response to the torquecommand and the power command. When NO in S14, the current output in thesingle-sided drive mode is sufficient, and there is no need to reducethe load on the first power source 11. Therefore, the process proceedsto S18, and the switching arbitrator 303 determines not to switchover tothe dual-sided drive mode.

Regarding the control modes selected in the dual-sided drive mode, inthe PWM control mode, multiple pulses corresponding to the carrier wavefrequency are output in one electrical cycle based on a comparison ofthe voltage command and the carrier wave, and in the rectangular wavecontrol mode, one pulse is output in one electrical cycle. The PWMcontrol mode includes a sine wave control mode and an overmodulationcontrol mode depending on the voltage utilization factor. Since thesecontrol modes are well known techniques, detailed description thereofwill be omitted. Moreover, the means and method for selecting a controlmode will not be described in detail because they are not included inthe scope of the specification.

The operation for switchover from the single-sided drive mode to thedual-sided drive mode will now be described in comparison with acomparative example and the first embodiment, with reference to the timecharts of FIGS. 9 and 10 . The power source voltages are equal, and thepower distribution ratio is 1:1. In the comparative example illustratedin FIG. 9 , no measures are taken to ensure continuity at the time ofdrive mode switching. In the first embodiment illustrated in FIG. 10 ,the above-described instantaneous correction and gradual change in powerlevel are performed as a measure for ensuring continuity at the time ofswitching.

Each drawing illustrates, in order from top to bottom, changes in thetorque of the MG 80, the rotational speed, the MG output, the voltageacross the MG coil ends, the power source current, the d-axis voltagecommand Vd, and the q-axis voltage command Vq. The MG output isproportional to the product of torque and rotational speed. The powersource voltage recognition value of each of the inverter controlcircuits 301 and 302 corresponds to the voltage across the MG coil ends.The vertical axis is provided with no specific value other than 0(zero). The quantities other than the d-axis current command Vd takezero or a positive value, and the d-axis current command Vd takes 0 or anegative value. The dot-and-dash lines in the drawings indicatequantities related to the first inverter, and the dashed-two dottedlines indicate quantities related to the second inverter. The sameapplies to the following time charts illustrating the switchingoperation.

In both FIGS. 9 and 10 , the drive mode switches from the first invertersingle-sided drive mode to the dual-sided drive mode, and then switchesfrom the dual-sided drive mode to the first inverter single-sided drivemode. Along with this, the amplitude of the voltage across the MG coilends switches from the first power source voltage VH1 to the voltage sum(VH1+VH2) of the two power sources, and then switches from the voltagesum (VH1+VH2) of the two power sources to the first power source voltageVH1.

In the first inverter single-sided drive mode, only the first powersource current Ib1 flows, and the second power source current Ib2 iszero. Therefore, the sum of the power source currents is Ib1+Ib2=Ib1. Inthe dual-sided drive mode, the current sum (Ib1+Ib2) of two powersources flows. In the first inverter single-sided drive mode, the firstvoltage command Vdq1 takes a non-zero value, and the second voltagecommand Vdq2 is zero. In the dual-sided drive mode, the first voltagecommand Vdq1 and the second voltage command Vdq2 take a same value thatis not zero.

At the time of the drive mode switching, the voltage across the MG coilends changes stepwise. At this time, in the comparative example in whicha measure is not taken to ensure continuity, the voltage commands Vdq1and Vdq2 suddenly change, and the torque and power fluctuate as insection (Xc). That is, the torque and the power change discontinuously.In contrast, in the first embodiment, the first voltage command Vdq1 isinstantaneously corrected for the stepwise change of the voltage acrossthe MG coil ends, and the second voltage command Vdq2 changes byfollowing this. Since the power level of the MG output is graduallychanged, the torque and the power do not fluctuate when the driving modeis switched, as indicated by the section (Xp). Therefore, the torque andthe power change while maintaining continuity.

The operation of the driving mode switching of FIG. 10 will be describedin the numerical order of 1 to 8. At operation 1, the first inverter 60performs single-sided drive. At operation 2, the power source voltagerecognition value switches from VH1 to (VH1+VH2) based on the switchingdetermination. At operation 3, the voltage command Vdq1 of the firstinverter 60 is instantaneously corrected based on the power sourcevoltage recognition values before and after the switching.

Then, the value to be transferred to the next integration cycle is setas an integral term based the values indicated by (*). As a specificexample, when there is an addition term different from the feedbackcontrol, the value is processed, e.g., subtracted and transferred, andset to an integral term that can maintain continuity between the controlcycles. The transferred value has the same effect as the PI integralterm. At operation 4, the switching arbitrator 303 gradually changes andincreases the output of the second inverter 70 from zero so that thefirst inverter 60 can respond.

At operation 5, the first inverter 60 and the second inverter 70 performdual-sided drive. At operation 6, the switching arbitrator 303 graduallychanges and decreases the output of the second inverter 70 to zero sothat the first inverter 60 can respond. At operation 7, the power sourcevoltage recognition value is switched from (VH1+VH2) to VH1 based on theswitching determination. At operation 8, the voltage command Vdq1 of thefirst inverter 60 is instantaneously corrected based on the power sourcevoltage recognition value. Then, the value set based on the voltagecommand Vdq1 applied immediately after the switchover from thesingle-sided drive mode is transferred to the next integration cycle.

FIG. 11 illustrates change in the power distribution of the inverters 60and 70 in the MG output at the time of drive mode switching. In thestable stage of the first inverter single-sided drive mode, the sharedpower of the first inverter 60 occupies 100%. In the power level gradualchange stage, the shared power of the second inverter 70 graduallyincreases. In the stable stage of the dual-sided drive mode, thedistribution ratio of the first inverter 60 and the second inverter 70is constant.

[Method of Determining Switching Between Single-Sided Drive Mode andDual-Sided Drive Mode]

A drive mode switching determination method capable of accurately (i.e.,reliably) and uniquely determining when the MG output reaches a targetoutput. Regarding the voltage utilization factor as a premise of theswitching determination, the voltage utilization factor in a typicalone-power source, one inverter configuration will now be described.

<One-Power Source, One-Inverter Configuration>

A drive mode switching request is assumed to be a switching requestcorresponding to a target or a scene such as the power source state (forexample, SOC), the temperature of the power sources, the inverters, orthe MG, or the MG output state (e.g., the voltage utilization factor).Among these factors, the voltage utilization factor, which is an indexindicating the MG output state, is calculated by the followingexpression. The line voltage amplitude corresponds to the peak value ofthe fundamental wave amplitude. The inverter input voltage is equal tothe power source voltage VH.

Voltage utilization factor=inverter line voltage amplitude/inverterinput voltage

Here, when the voltage utilization factor is VUF, the conversioncoefficient is K, and the dq axis voltage amplitude is |Vdq|, the aboveexpression is represented as expression (2). Note that, since theconversion coefficient K is uniquely determined by determining how thevoltage utilization factor is expressed, it is omitted from thefollowing expressions including FIGS. 12A and 12B.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 2} \right\rbrack & \; \\{{VUF} = {K \times \frac{{Vdq}}{VH}}} & (2)\end{matrix}$<Two-Power Source, Two-Inverter Configuration>

In the dual-sided drive mode of the two-power source, two-inverterconfiguration, the voltage utilization factor used for MG control iscalculated by dividing the inverter line voltage for each inverter bythe sum of the two-power source voltages, as in the followingexpression.

Voltage utilization factor used for MG control=inverter line voltage/sumof two-power source voltage

The voltage utilization factor used for MG control is the voltageutilization factor in the MG viewpoint utilized for grasping the controlstate, and, hereinafter, denoted by the symbol VUF_MG. Voltageutilization factors VUF_MG_INV1 and VUF_MG_INV2 used for MG control ofthe respective inverters are represented by expressions (3.1) and (3.2)using the dq-axis voltages Vdq1 and Vdq2.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 3} \right\rbrack & \; \\{{{VUF\_ MG}{\_ INV}\; 1} = \frac{{{Vdq}\; 1}}{{{VH}\; 1} + {{VH}\; 2}}} & (3.1) \\{{{VUF\_ MG}{\_ INV}\; 2} = \frac{{{Vdq}\; 2}}{{{VH}\; 1} + {{VH}\; 2}}} & (3.2)\end{matrix}$

FIG. 12A illustrates the operation of switching determination using thevoltage utilization factor VUF_MG used for MG control. In the firstinverter single-sided drive mode, when the first inverter voltageutilization factor VUF_MG_INV1 increases and reaches a two-sideswitching threshold, the VUE drive mode switches to dual-sided drivemode. At this time, the second inverter voltage utilization factorVUF_MG_2 increases stepwise from zero, and the first inverter voltageutilization factor VUF_MG_INV1 decreases stepwise.

In the dual-sided drive mode, the voltage utilization factor VUF_MG_INV1and VUF_MG_INV2 of both inverters increase together, reach the upperlimit, and then decrease together. Subsequently, when the voltageutilization factor VUF_MG_INV1 and VUF_MG_INV2 of both inverters reach aone-side switching threshold, the drive mode switches to the firstinverter single-sided drive mode.

Switching determination using a self-inverter voltage utilization factorVUF self as another voltage utilization factor will now be described.The self-inverter voltage utilization factor is calculated by dividingthe inverter line voltage for each inverter by input voltage of eachinverter, as in the following expression.

Self-inverter voltage utilization factor=inverter line voltage/inverterinput voltage Hereinafter, the self-inverter voltage utilization factoris denoted by the symbol VUF self Self-inverter voltage utilizationfactors VUF self INV1 and VUF self INV2 of the respective inverters areexpressed by expression (4.1) and (4.2) using dq-axis voltages Vdq1 andVdq2.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 4} \right\rbrack & \; \\{{{VUF\_ self}{\_ INV1}} = \frac{{{Vdq}\; 1}}{{VH}\; 1}} & (4.1) \\{{{VUF\_ self}{\_ INV2}} = \frac{{{Vdq}\; 2}}{{VH}\; 2}} & (4.2)\end{matrix}$

For example, when operation is performed in the single-sided drive modeto the limit, the upper threshold of the self-inverter voltageutilization factor VUF self refers to the output limit of one inverterin switching drive. That is, by determining the switching timing usingthe self-inverter voltage utilization factor VUF self, it can bedetermined whether the region is one in which a desired output can beobtained by one inverter. That is, by comparing the self-invertervoltage utilization factor VUF self and a threshold reflecting a desiredvoltage utilization factor, the switching timing of the single-sideddrive mode and the dual-sided drive mode can be determined with respectto the MG output state.

According to this method, even if a variation in the device constantoccurs due to errors of the sensors, change in the MG magnetic flux dueto the temperature characteristic, etc., a target switching point can becorrectly determined while taking into consideration the state. It ispreferable to prevent hunting of switching by providing hysteresis inthe threshold value used for the switchover from the single-sided drivemode to the dual-sided drive mode and the threshold value used for theswitchover from the dual-sided drive mode to the single-sided drivemode.

FIG. 12B illustrates the operation of switching determination using theself-inverter voltage utilization factor VUF self. In the first invertersingle-sided drive mode where VH2=0, the self-inverter voltageutilization factor VUF self INV1 of the first inverter is equal to thevoltage utilization factor VUF_MG_INV1. When the self-inverter voltageutilization factor VUF self INV1 increases and reaches the two-sideswitching threshold, the drive mode switches to the dual-sided drivemode. At this time, the self-inverter voltage utilization factor VUFself INV1 of the first inverter increases stepwise.

The operation of the voltage utilization factors VUF_MG_INV1 andVUF_MG_INV2 in the dual-sided drive mode is the same as that of FIG.12A. Even if the voltage utilization factors VUF_MG_INV1 and VUF_MG_INV2of both inverters fall below the upper limit, they do not pertain to theswitching determination. When the self-inverter voltage utilizationfactor VUF self INV1 reaches the one-side switching threshold, the drivemode switches to the first inverter single-sided drive mode.

[Effects]

(1) The switching arbitrator 303 of the first embodiment arbitrates theoutputs of the respective inverters 60 and 70 at the time of switchingso that the MG outputs before and after drive mode switching continue.Consequently, the MG control device 101 can stabilize and ensurecontinuity of the MG output at the time of switching between thesingle-sided drive mode and the dual-sided drive mode in the two-powersource, two-inverter configuration. Furthermore, it is possible toprevent failure of components due to overcurrent caused by excessivevoltage application.

(2) In specific, at the time of switchover from the single-sided drivemode to the dual-sided drive mode, the switching arbitrator 303gradually changes and increases the power level of the drive-start-sideinverter from zero. At the time of switchover from the dual-sided drivemode to the single-sided drive mode, the switching arbitrator 303gradually changes and decreases the power level of the drive-end-sideinverter to zero. Consequently, changes in the output of the inverterscan be mitigated at the rising edge and falling edge at the time ofdrive mode switching, and fluctuation in the torque of the motor causedby the influence of power fluctuation can be eliminated.

(3) The switching arbitrator 303 performs switching determination inaccordance with an output request to the MG 80, the SOC state of thepower sources 11 and 12, or the temperature of the power source 11 and12, the inverters 60 and 70, or the MG 80. Consequently, it is possibleto determine whether the drive mode can be switched in accordance withthe drive state.

(4) The switching arbitrator 303 determines the switching between thesingle-sided drive mode and the dual-sided drive mode based on theself-inverter voltage utilization factor VUF self calculated by dividingthe inverter line voltage by the inverter input voltage for at least oneof the inverters. Consequently, a switching threshold can be setindependently of the power source voltage difference, and the switchingdetermination can be uniquely executed.

(5) The first embodiment provides a control configuration in which, inthe single-sided drive mode, the output of the inverters is determinedbased on one of the power source voltages, and in the dual-sided drivemode, the output of the respective inverters is determined based on thesum of the two-power source voltages. At the time of the drive modeswitching, the switching arbitrator 303 instantaneously corrects thevoltage command Vdq1 in response to sudden change in the sum of thetwo-power source voltages and transfers it to the next processing cycle.Consequently, in the first embodiment, the influence of sudden change involtage at the time of drive mode switching can be suppressed, andstable inverter drive can be achieved.

Second Embodiment

The second embodiment will now be described with reference to FIG. 13 .Similar to the first embodiment, the second embodiment has a controlconfiguration in which, in the single-sided drive mode, the output ofthe inverters is determined based on one of the power source voltages,and in the dual-sided drive mode, the output of the respective invertersis determined based on the sum of the two-power source voltages. In thesecond embodiment, the switching arbitrator 303 executes a slow changeprocess for gradually changing the voltage recognition value for controlin response to a sudden change in the sum of the two-power sourcevoltages as a response means for a stepwise change due to instantaneoussuperposition of the output pulse voltages of the inverters 60 and 70 atthe time of drive mode switching.

Specifically, in the slow change process, the amount of change per timeof the power source voltage recognition value is limited by an arbitrarytime constant delay filter or rate processing. That is, whileinstantaneous voltage correction is performed in the first embodiment,continuous voltage correction is performed in the second embodiment tosuppress output fluctuation.

FIG. 13 illustrates the operation of the slow change process in thetransition from the first inverter single-sided drive mode to thedual-sided drive mode and the transition from the dual-sided drive modeto the first inverter single-sided drive mode. The first inverter 60executes the slow change process of operations 1 and 4, and the secondinverter 70 executes the slow change process of operations 2 and 3.

When the first inverter single-sided drive mode is switched to thedual-sided drive mode, at operation 1, the switching arbitrator 303switches the power source voltage recognition value of the firstinverter 60 from VH1 to (VH1+VH2) through the gradual change process. Atoperation 2, the switching arbitrator 303 gradually changes andincreases the output of the second inverter 70 at the rising edge fromthrough the slow change process. Along with this, the output of thefirst inverter 60 is made to respond without difficulty so as to shiftto a stable dual-sided drive mode.

When the dual-sided drive mode is switched to the first invertersingle-sided drive mode, at operation 3, the switching arbitrator 303switches the power source voltage recognition value of the secondinverter 70 from (VH1+VH2) to VH1 through the gradual change process. Atoperation 4, the switching arbitrator 303 gradually changes anddecreases the output of the second inverter 70 at the rising edge tozero through the slow change process. Along with this, the output of thefirst inverter 60 is made to respond without difficulty so as to shiftto a stable single-sided drive mode. Thus, in the second embodiment, theinfluence of sudden change in voltage at the time of drive modeswitching can be suppressed, and stable inverter drive can be achieved.

Third Embodiment

The control configuration according to the third embodiment relating toswitchover from a single-sided drive mode by one inverter to asingle-sided drive mode by the other inverter will now be described withreference to FIGS. 14A to 18 . For example, if only one power source iscontinuously used in the single-sided drive mode under low load, thepower consumption becomes biased, and the power source temperaturerises. In the case where the power source is a battery, the SOC maybecome biased and depleted. Therefore, it is effective to switch thepower source being used by stopping the inverter that is being driven inthe single-sided drive mode and driving the inverter that has beenstopped in the single-sided drive mode.

In such switchover from the first inverter single-sided drive mode tothe second inverter single-sided drive mode, the voltage across the MGcoil ends always changes between before and after the switching due to apower source voltage difference and various machine differencesincluding the inverters, regardless of the control method. This is anunavoidable problem in the two-power, two-inverter system. If the systemcannot respond to such change in the voltage across ends of the MG coil,which is directly connected to the generation of three-phase current,excessive or insufficient voltage required for causing desired currentto flow is generated across the MG coil ends, and current disturbancewill readily occur due to the relationship between the electric circuitsand the pulse voltage outputs.

As illustrated in FIG. 14A, the amplitude of the voltage across the MGcoil ends is the voltage amplitude VH1 of the first power source 11 infirst inverter one-side driving, and the voltage amplitude VH2 of thesecond power source 12 in second inverter one-side driving. Here, as thevoltage ratio of the two power sources, the ratio of the second powersource voltage VH2 to the first power source voltage VH1 is denoted bya. For example, when the first power source voltage VH1 is 200 V and thesecond power source voltage VH1 is 400 V, α is 2.

FIG. 14B illustrates a schematic control configuration at the time ofswitchover from the first inverter single-sided drive mode to the secondinverter single-sided drive mode. During switching drive by only thefirst inverter 60, the first power source voltage VH1 is applied as aninput voltage for PWM control. In contrast, during switching drive onlyby the second inverter 70, the second power source voltage VH2 isapplied as an input voltage for PWM control. Therefore, if there is anexcess or shortage of applied voltage occurs at the time of drive modeswitching relative to the voltage immediately before the switchover, theinverter output is not appropriately transferred, and currentdisturbance occurs.

Therefore, in the third embodiment, the dual-sided drive mode is enteredbefore switching between the first inverter single-sided drive mode andthe second inverter single-sided drive mode in order to eliminate thepower source voltage difference and machine difference. In thedual-sided drive mode, the inverter control circuit 301 and 302 generateinverter voltage commands Vdq1 and Vdq2, respectively, in considerationof the power source voltage difference and the machine difference.

FIG. 15A illustrates an example of a control configuration of switchoverfrom the first inverter single-sided drive mode to the second invertersingle-sided drive mode. At the time of switchover from the firstinverter single-sided drive mode to the dual-sided drive mode, thevoltage command Vdq1 of the first inverter 60 is multiplied by(VH1+VH2)/VH1 (=1+α), which is the ratio of the voltage recognitionvalues before and after the switchover through instantaneous correctionof the power source voltage recognition values.

In the dual-sided drive mode, power distribution control is performed soas to gradually change the power level of the first inverter 60. At thestart of the dual-sided drive mode, the voltage command Vdq1 of thefirst inverter 60 is equal to the MG output, and the voltage commandVdq2 of the second inverter 70 is zero. At the end of the dual-sideddrive mode, the voltage command Vdq1 of the first inverter 60 is zero,and the voltage command Vdq2 of the second inverter 70 is equal to theMG output. During this time, output arbitration is performed.

At the time of switchover from the dual-sided drive mode to the secondinverter single-sided drive mode, the ratio of the voltage recognitionvalues before and after the switchover, VH2/(VH1+VH2), is multiplied andtransferred as the voltage command Vdq2 of the second inverter 70through the instantaneous correction of the power source voltagerecognition values. The value of the ratio is converted as in expression(5).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 5} \right\rbrack & \; \\{\frac{{VH}\; 2}{{{VH}\; 1} + {{VH}\; 2}} = \frac{\alpha}{1 + \alpha}} & (5)\end{matrix}$

As described above, in the case of switchover from the single-sideddrive mode by one inverter to the single-sided drive mode by the otherinverter, the switching arbitrator 303 transfers a value obtained bymultiplying the voltage command Vdq1 output by the drive-end-sideinverter by a correction coefficient based on the voltage ratio α of thetwo power sources as the voltage command Vdq2 of the drive-start-sideinverter.

As illustrated in FIG. 15B, the switching arbitrator 303 graduallydecreases the output (i.e., the power level) of the first inverter 60 onthe drive-end-side from 100% to 0% while in the dual-sided drive mode,and gradually increases the output of the second inverter 70 on thedrive-start-side from 0% to 100% to transfer the power level. At thistime, the power is gradually changed at a changing rate level that canbe followed by the feedback control. When the output of the firstinverter 60 falls 0%, the switching arbitrator 303 stops the firstinverter 60.

The drive mode switching process according to the third embodiment willbe described with reference to the flowchart of FIG. 16 . In FIG. 16 ,descriptions of the steps corresponding to the steps in FIG. 6 will beappropriately omitted. The determination of switchover from thesingle-sided drive mode to the dual-sided drive mode in step S10, andprocesses from the setting of the voltage recognition value to thegradual change in the power level in steps S21 to S24 are basically thesame as those in FIG. 6 .

For example, when the temperature Hb1 of the first power source 11 risesexcessively, through the switching determination in step S10, theswitching arbitrator 303 determine switchover to stop the first inverter60 in one-side driving and alternatively start one-side driving of theinverter that has been stopped up to the present. Here, the phrase whenthe temperature rises excessively refers to a case in which thetemperature exceeds the allowable upper limit that is higher than theappropriate upper limit in step S12 of FIG. 8 . In such a case, it ispreferable not only to reduce the load on the first power source 11 inthe dual-sided drive mode but also to stop the first inverter 60 moreactively. Note that it is preferable to carry out the same measure whenthe temperature Hinv1 of the first inverter 60 rises excessively.

Also, in a case where the SOC of the first power source 11 falls belowthe allowable lower limit that is lower than the appropriate lower limitin step S13 of FIG. 8 , it is preferable that the switching arbitrator303 stop the first inverter 60 by switching to the second invertersingle-sided drive mode instead of staying in the dual-sided drive mode.

In step S25, the switching arbitrator 303 establishes settings to switchthe roles of the two inverter control circuits 301 and 302 as a torquemanagement circuit and a power management circuit. As described above,the torque management circuit performs feedback control. The powermanagement circuit performs power distribution control on a feedforwardcontrol base, and manages the distribution of power supplied from thetwo power sources 11 and 12 to the two inverters 60 and 70.

The inverter control circuit that switches from feedback control tofeedforward control inherits the value of the integral term as aninitial value for power control, and thus starts the power control atthis time point. The inverter control circuit that switches fromfeedforward control to feedback control substitutes the voltage commandused for the power control into the integral term to transfer thevoltage command to the feedback control, and starts the feedback controlwith the resulting value as the initial value.

In step S30, as in step S10, the switchover from the dual-sided drivemode to the single-sided drive mode is determined. When the switchingdetermination holds and YES is determined in step S30, the respectiveprocesses from the setting of the voltage recognition value to thegradual change in the power level are performed in S41 to S44, as in S21to S24. In S45, the roles of the two inverter control circuits 301 and302 are set as in S25.

The time chart in FIG. 17 illustrates the operation of switching fromthe first inverter single-sided drive to the second invertersingle-sided drive in the case where the voltages of the two powersources are equal (i.e., α=1), and the switching operation is explainedin numerical order of the periods 1 to 9. At operation 1, the firstinverter 60 performs single-sided drive. At operation 2, the powersource voltage recognition value switches from VH1 to (VH1+VH2) based onthe switching determination. At operation 3, the voltage command Vdq1 ofthe first inverter 60 is instantaneously corrected based on the powersource voltage recognition value. At operation 4, the switchingarbitrator 303 gradually changes and increases the output of the secondinverter 70 from zero so that the first inverter 60 can respond.

At operation 5, the first inverter 60 and the second inverter 70 performdual-sided drive. At operation 6, the switching arbitrator 303 graduallychanges and increases the output of the second inverter 70 to 100% sothat the first inverter 60 can respond. At operation 7, the power sourcevoltage recognition value is switched from (VH1+VH2) to VH2 based on theswitching determination.

At operation 8, a value obtained by multiplying the voltage command Vdq1output from the first inverter 60 by a correction coefficient based onthe voltage ratio α of the two power sources is transferred as thevoltage command Vdq2 of the second inverter 70 through instantaneouscorrection based on the power source voltage recognition value. Atoperation 9, the control method of the second inverter control circuit302 is switched from feed-forward control-based power control to afeedback control method.

The time chart of FIG. 18 illustrates the operation of switching fromthe first inverter single-sided drive to the second invertersingle-sided drive in the case where the voltages of the two powersources are different. In this example, the second power source voltageVH2 is higher than the first power source voltage VH1, and the voltageratio α of the two power sources is greater than one. The powerdistribution ratio is 1:1. The numbered periods 1 to 9 of respectiveoperations are in accordance with FIG. 17 , and only the differencesfrom FIG. 17 will be described.

At the time of switchover from the first inverter single-sided drivemode to the dual-sided drive mode of operation 2, the difference betweenthe voltage recognition values before and after the switchover, VH1 and(VH1+VH2), is large. Therefore, the change of the voltage command Vdq1due to the instantaneous correction of the operation 3 appearsrelatively large in the MG viewpoint. At the time of switchover from thedual-sided drive mode to the second inverter single-sided drive mode ofoperation 7, the difference between the voltage recognition valuesbefore and after the switchover, (VH1+VH2) and VH2, is small. Therefore,the change of the voltage command Vdq2 due to the instantaneouscorrection of the operation 8 appears relatively small in the MGviewpoint. At this time, the value multiplied by the correctioncoefficient based on the voltage ratio α of the two power sources istransferred as the voltage command Vdq2 of the second inverter 70.

In the third embodiment, as in the first embodiment, output fluctuationat the time of drive mode switching can be eliminated, and the SOCdepletion of only one power source can be avoided when the single-sideddrive mode with low load and low loss is continued.

At least one of the inverter control circuits operates as the powermanagement circuit, and the switching arbitrator 303 switches the roleof the power management circuit between the two inverter controlcircuits 301 and 302 and transfers the last control state to the otherside at the time of drive mode switching. Consequently, the invertercontrol circuit that performs power distribution in the dual-sided drivemode is fixed, and the number of state transitions can be reduced tosimplify the configuration.

Note that switching of the role of the power management circuit betweenthe two inverter control circuits 301 and 302 is the same as in thefirst and second embodiments described above. That is, the roles of thetorque management circuit and the power management circuit may beswitched at the time of switchover from the first inverter single-sideddrive mode to the dual-sided drive mode and the time of switchover fromthe dual-sided drive mode to the first inverter single-sided drive mode.

Fourth Embodiment

The fourth embodiment will now be described with reference to FIGS. 19to 21 . FIG. 19 illustrates the overall configuration of a system towhich an MG control device 104 of the fourth embodiment is applied. Inthis system, the two inverters 60 and 70 are connected to one commonpower source 13. The reference signs of a capacitor 16, a voltage sensor18, and a temperature sensor 861, which are so provided as to correspondto the common power source 13, are denoted by the reference signs of therespective components corresponding to the first power source 11 of thefirst embodiment. The voltage sensor 18 detects the voltage VH of thecommon power source 13, and the temperature sensor 861 detects thetemperature Hb of the common power source 13. The current flowingthrough the common power source 13 is referred to as common power sourcecurrent Ib. The power Pb of the common power source 13 is expressed byPb=Ib×VH.

The high-potential-side wirings P1 and P2 of the first inverter 60 andthe second inverter 70 are connected to each other through a commonhigh-potential-side wiring Pcom, and the low-potential-side wirings N1and N2 are connected to each other through a common low-potential-sidewiring Ncom. A switch 14 capable of interrupting a current path isdisposed in at least one of the common high-potential-side wiring Pcomand the common low-potential-side wiring Ncom. In the example of FIG. 19, the switch 14 is disposed in the common high-potential-side wiringPcom.

As in FIG. 1 of the first embodiment, current Ib1 flows through thefirst inverter 60, and current Ib2 flows through the second inverter 70.However, in the fourth embodiment, the reference sign Ib1 does notdenote the current of the first power source but the input current ofthe first inverter. Similarly, the reference sign Ib2 does not denotethe current of the second power source but the input current of thesecond inverter.

The sum of the shared power P_INV1 of the first inverter 60 and theshared power P_INV2 of the second inverter 70 is substantially equal tothe power Pb of the common power source 13, although there is a slightdifference when the loss due to wiring or the like is taken intoconsideration. That is, Pb P_INV1+P_INV2. If current and voltage areused, Ib×VH≈Ib1×VH+Ib2×VH.

The configuration of the control unit 300 is basically the same as thatof the first embodiment. However, while at least one of the invertercontrol circuits has a function of adjusting the level of power suppliedfrom the two power sources 11 and 12 to the two inverters 60 and 70 inthe first embodiment, the level of power supplied from the common powersource 13 to the two inverters 60 and 70 is adjusted in the fourthembodiment. In such a case, the shared powers P_INV1 and P_INV2 areadjusted by adjusting the currents Ib1 and Ib2 input to the inverters 60and 70.

In a star connection circuit configured by establishing neutral pointcoupling of one inverter, the MG control device 104 can operate theother inverter in the single-sided drive mode in an open (i.e., off)state of the switch 14. Moreover, in the dual-sided drive mode, the MGcontrol device 104 can operate an H-bridge circuit including firstswitching elements 61 to 66 and second switching elements 71 to 76 ofthe phases in a closed (i.e., on) state of the switch 14. As describedabove, a technique of switching between the star connection circuit andthe H-bridge circuit through operation of the switch 14 is disclosed inJP 2017-175747 A, etc.

FIG. 20A illustrates switching drive in a star connection circuit in thesingle-sided drive mode. For example, by turning on one of upper-armswitching elements 71, 72, and 73 of all phases and lower-arm switchingelements 74, 75, and 76 of all phases of the second inverter 70 andturning off the other, neutral point coupling is established, and a starconnection circuit is formed by three-phase windings 81, 82, and 83. Thefirst inverter 60 is then driven in the single-sided drive mode.

FIG. 20B illustrates switching drive of the H-bridge circuit in thedual-sided drive mode. An H-bridge circuit is formed by the switchingelements 61 and 64 of the first inverter 60 and the switching elements71 and 74 of the second inverter 70 with respect to the U-phase openwinding 81. An H-bridge circuit is formed by the switching elements 62and 65 of the first inverter 60 and the switching elements 72 and 75 ofthe second inverter 70 with respect to the V-phase open winding 82. AnH-bridge circuit is formed by the switching elements 63 and 66 of thefirst inverter 60 and the switching elements 73 and 76 of the secondinverter 70 with respect to the W-phase open winding 83. By driving theH-bridge circuits of the respective phases in the dual-sided drive mode,a double value of the common power source voltage VH is applied to theMG80.

FIG. 21 is a time chart illustrating a drive mode switching operationaccording to the fourth embodiment. As in FIG. 10 of the firstembodiment, the drive mode is switched from the first invertersingle-sided drive mode to the dual-sided drive mode, and then switchedfrom the dual-sided drive mode to the first inverter single-sided drivemode. The changes in the torque, the rotational speed, and the MG outputof the MG 80 are the same as those in FIG. 10 . For the amplitude of theMG coil end voltage, the first power source voltage VH1 of FIG. 10 isreplaced by the common power source voltage VH, and the sum of thetwo-power source voltages (VH1+VH2) is replaced by a double value of thecommon power source voltage (VHx2).

With respect to the power source current in FIG. 10 , in FIG. 21 , theprofile of change is the same, but a change in the inverter inputcurrent or the inverter shared power proportional to the input currentis shown instead of that of the power source current. The sum of thetwo-power source voltages (Ib1+Ib2) of FIG. 10 is replaced by the commonpower source current Ib. The sum of the shared power of the twoinverters 60 and 70 (P_INV1+P_INV2) changes in proportion to the changein the common power source current Ib. The instantaneous correction ofthe voltage commands Vdq1 and Vdq2 at the time of drive mode switchingis the same as that of FIG. 10 and thus a description thereof will beomitted.

The MG control device 104 in this switching control determines theoutput of one inverter (e.g., the first inverter 60) based on the commonpower source voltage VH in the single-sided drive mode, and determinesthe output of the respective inverters 60 and 70 based on the doublevalue of the common power source voltage (VH×2) in the dual-sided drivemode. At the time of drive mode switching, the switching arbitrator 303instantaneously corrects the voltage commands Vdq1 and Vdq2 in responseto sudden change in the voltage used for the determination of the outputof the inverters, i.e., sudden change from VH to (VH×2) or from (VH×2)to VH, and transfers the voltage commands to the next processing cycle.

The slow change process according to the second embodiment may becombined with the above-described switching control according to thefourth embodiment. In such a case, the switching arbitrator 303 executesthe slow change process in which the voltage recognition value for thecontrol is slowly changed in response to sudden change in the voltageused for the determination of the output of the inverters at the time ofdrive mode switching.

As described above in the fourth embodiment, the single-sided drive modeof the star connection circuit and the dual-sided drive mode of theH-bridge circuit are switched in the system for driving the MG 80including the open windings 81, 82, and 83 by using one common powersource 13 and two inverters 60 and 70. Then, the output of the powerP_INV1 and the power P_INV2 shared by the respective inverters 60 and 70is arbitrated at the time of drive mode switching in accordance with thedrive mode after the drive mode switching.

Consequently, one inverter can be stably stopped in the drive region ofMG low output to reduce loss. When the thermal load of one inverter ishigh in the single-sided drive mode or the dual-sided drive mode, aninverter on one side can be stably stopped or shifted to the dual-sideddrive mode to distribute the thermal load.

In addition, the switching arbitrator 303 of the fourth embodimentachieves the same effects as the effects (2) to (4) of the firstembodiment. That is, at the time of the switchover from the single-sideddrive mode to the dual-sided drive mode, the switching arbitrator 303gradually changes and increases the level of power of thedrive-start-side inverter from zero. At the time of switchover from thedual-sided drive mode to the single-sided drive mode, the switchingarbitrator 303 gradually changes and decreases the power level of thedrive-end-side inverter to zero. Consequently, changes in the output ofthe inverters can be mitigated at the rising edge and falling edge atthe time of drive mode switching, and fluctuation in the torque of themotor caused by the influence of power fluctuation can be eliminated.

The switching arbitrator 303 performs switching determination inaccordance with an output request to the MG 80, the SOC state of thecommon power source 13, or the temperature of the common power source13, the inverters 60 and 70, or the MG 80. Consequently, it is possibleto determine whether the drive mode can be switched in accordance withthe drive state.

The switching arbitrator 303 determines the switching between thesingle-sided drive mode and the dual-sided drive mode based on theself-inverter voltage utilization factor VUF self calculated by dividingthe inverter line voltage by the inverter input voltage for at least oneinverter.

Consequently, a switching threshold can be set independently of thepower source voltage difference, and the switching determination can beuniquely executed.

Furthermore, in the fourth embodiment, as in the above embodiments, atleast one of the inverter control circuits operates as a powermanagement circuit. In such a case, the switching arbitrator 303 canswitch the role of the power management circuit between the two invertercontrol circuits 301 and 302 at the time of drive mode switching, andtransfer the last control state to the other side.

Fifth Embodiment

The fifth embodiment will now be described with reference to FIG. 22 .FIG. 22 illustrates the overall configuration of a system to which an MGcontrol device 105 of the fifth embodiment is applied. In such a system,as in the first embodiment illustrated in FIG. 1 , the first inverter 60is connected to the first power source 11, and the second inverter 70 isconnected to the second power source 12. The meanings of the first powersource current Ib1, the second power source current Ib2, the firstsource voltage VH1, and the second source voltage VH2 are interpreted inaccordance with the first embodiment.

An MG 90 of the fifth embodiment is a six-phase dual winding motorincluding a first winding set 910 and a second winding set 940, eachhaving three phases. In the first winding set 910, U-phase, V-phase, andW-phase windings 91, 92 and 93 are star-connected, and in the secondwinding set 940, X-phase, Y-phase, and Z-phase windings 94, 95 and 96are star-connected.

The first inverter 60 includes multiple first switching elements 61 to66 that receive DC power from the first power source 11 and are sodisposed as to correspond to the phases of the first winding set 910,and is connected to the first winding set 910. A U-phase voltage VU, aV-phase voltage VV, and a W-phase voltage VW are applied from the firstinverter 60 to the respective phase windings 91, 92, and 93 of the firstwinding set 910.

The second inverter 70 includes multiple second switching elements 71 to76 that receive DC power from the second power source 12 and are sodisposed to correspond to the phases of the second winding set 940, andis connected to the second winding set 940. An X-phase voltage VX, aY-phase voltage VY, and a Z-phase voltage VZ are applied from the secondinverter 70 to the respective phase windings 94, 95, and 96 of thesecond winding set 940.

In addition, the configuration of the control unit 300, the temperaturesensor 861 to 865, etc., of the fifth embodiment is the same as that ofthe first embodiment. In the fifth embodiment, the drive mode switchingcontrol substantially the same as that according to the first to thirdembodiments can be applied, and similar effects can be achieved.

Sixth Embodiment

The sixth embodiment will now be described with reference to FIGS. 23and 24 . FIG. 23 illustrates the overall configuration of a system towhich an MG control device 106 of the sixth embodiment is applied. Inthis system, the two inverters 60 and 70 are connected to the one commonpower source 13, as in the fourth embodiment illustrated in FIG. 19 .The meanings of the first inverter input current Ib1, the secondinverter input current Ib2, and the common power source voltage VH areinterpreted in accordance with the fourth embodiment. The MG 90 of thesixth embodiment is a six-phase dual winding motor as in the fifthembodiment.

The high-potential-side wirings P1 and P2 of the first inverter 60 andthe second inverter 70 are connected to each other through a commonhigh-potential-side wiring Pcom, and the low-potential-side wirings N1and N2 are connected to each other through a common low-potential-sidewiring Ncom. The relationship between the power Pb of the common powersource 13 and the shared power P_INV1 and P_INV2 of the inverters 60 and70 is also expressed as Pb≈P_INV1+P_INV2 and Ib×VH≈Ib1×VH+Ib2×VH inaccordance with the fourth embodiment. In the configuration of thecontrol unit 300, as in the fourth embodiment, at least one invertercontrol circuit has a function of adjusting the level of the powersupplied from the common power source 13 to the two inverters 60 and 70.

FIG. 24 is a time chart illustrating a drive mode switching operationaccording to the sixth embodiment. As in FIGS. 10 and 21 of the firstand fourth embodiments, the drive mode is switched from the firstinverter single-sided drive mode to the dual-sided drive mode, and thenswitched from the dual-sided drive mode to the first invertersingle-sided drive mode. The change in the torque, the rotational speed,and the MG output of the MG 80 is the same as that of FIGS. 10 and 21 ,and the inverter input current or the inverter shared power proportionalto the input current is the same as that of FIG. 21 .

The amplitude of the voltage across the MG coil ends remains constant atthe common power source voltage VH regardless of the switching betweenthe single-sided drive mode and the dual-sided drive mode. Therefore, inthe sixth embodiment, the voltages used for the determination of theoutput of the inverter do not suddenly change, and thus there is no needto consider the instantaneous correction of the voltage command or thegradual change process.

As described above in the sixth embodiment, the single-sided drive modeand the dual-sided drive mode are switched in the system for driving theMG 80 having six-phase dual windings by using the common power source 13having one winding and the two inverters 60 and 70. Then, the output ofthe power P_INV1 and the power P_INV2 shared by the respective inverters60 and 70 is arbitrated at the time of drive mode switching inaccordance with the drive mode after the drive mode switching.

Consequently, in scenes in which low-loss operation is possible bystopping the inverter based on the element loss characteristics and theshared current level, an inverter on one side can be stably stopped orshifted to the dual-sided drive mode to reduce loss. When the thermalload of one inverter is high in the single-sided drive mode or thedual-sided drive mode, an inverter on one side can be stably stopped orshifted to the dual-sided drive mode to distribute the thermal load.

In addition, the switching arbitrator 303 of the sixth embodimentachieves the same effects as the effects (2) to (4) of the firstembodiment. This point is the same as that described in the fourthembodiment. The role of the power management circuit is switched betweenthe two inverter control circuits 301 and 302 in the same manner as inthe above-described embodiments.

Other Embodiments

(a) In the above-described embodiments, the drive mode switching isdetermined basically based on an MG output request and the power sourcestate. In another embodiment, in addition to these factors, a fail-safetransition request based on detection of failure or signs of failure inthe power sources 11 and 12 and the inverters 60 and 70 may beconsidered.

(b) In the system configuration of the first and fifth embodiments inwhich two independent power sources are used, either of the powersources is not limited to a secondary battery represented by a batteryor a capacitor. For example, one power source may be a secondarybattery, and the other power source may be a fuel cell or a generator.

(c) The number of phases of the open windings of the motor according tothe first and fourth embodiments is not limited to three but may be fouror more. Alternatively, two-phase open windings may be bridge-connected.

(d) The number of phases of the respective winding sets in themulti-phase dual motor according to the fifth and sixth embodiments isnot limited to three phases but may be four or more. The configurationof each winding set is not limited to a star connection but may be adelta connection.

(e) The two-power, two-inverter type electric motor drive device isapplicable to pure electric vehicles, such as electric vehicles and fuelcell vehicles, as well as electrically-rich hybrid power trains such asplug-in hybrid (PHV) and range extenders, and light electric vehicles,such as 12 to 48 V integrated starter generators (ISGs). This technologyis based on voltage-type circuit topology that can be applied to usesthat achieve high power output with high efficiency by serializing thepower source voltages without using any voltage boost circuit with areactor, which is a known conventional technology. This technology issuitable for applications in which high power output is required even inregions that are thermally difficult to achieve with conventional boostcircuits and high-current type inverters in each vehicle, and enablesmore efficient operation than conventional powertrains.

The disclosure is not limited in any way to the above-describedembodiments, and various modes can be implemented without departing fromthe scope thereof.

The control unit and methods described in the disclosure may beimplemented by a dedicated computer provided by configuring a processorand a memory programmed to perform one or more functions embodied by acomputer program. Alternatively, the control units and methods describedin the disclosure may be implemented by a dedicated computer provided byconfiguring a processor with one or more dedicated hardware logiccircuits. Alternatively, the control units and methods described in thedisclosure may be implemented by one or more dedicated computersconfigured by a combination of a processor and a memory programmed toperform one or more functions and a processor configured by one or morehardware logic circuits. The computer program may also be stored in acomputer-readable non-transitive tangible recording medium asinstructions to be executed by a computer.

The disclosure is described in accordance with embodiments. However, thedisclosure is not limited to such embodiments and structures. Thedisclosure also encompasses various variants and variations within thescope of equality. Various combinations and modes, as well as othercombinations and modes including only one element, more or less,thereof, are also within the scope and idea of the disclosure.

What is claimed is:
 1. An electric motor drive device that controlsdriving of a motor including open windings of two or more phases byusing two inverters individually connected to two power sources, theopen windings having end points that are open to each other, theelectric motor drive device comprising: a first inverter that receivesDC power from a first power source, includes a plurality of firstswitching elements so disposed as to correspond to the phases of theopen windings, and is connected to one ends of the open windings; asecond inverter that receives DC power from a second power source,includes a plurality of second switching elements so disposed as tocorrespond to the phases of the open windings, and is connected to otherends of the open windings; and a control unit comprising: two invertercontrol circuits of a first inverter control circuit that generates afirst voltage command and a second inverter control circuit thatgenerates a second voltage command, based on a torque command, the firstvoltage command being an output voltage command to the first inverter,the second voltage command being an output voltage command to the secondinverter; and a switching arbitrator that determines switching between asingle-sided drive mode and a dual-sided drive mode and arbitratesoutput of each of the inverters at a time of switching for making outputof the motor continuous before and after the switching between the drivemodes, the single-sided drive mode being a mode in which one of the twoinverters performs switching drive, the dual-sided drive mode being amode in which both the two inverters performs switching drive, wherein,at least one of the inverter control circuits has a function ofadjusting a level of power supplied from the two power sources to thetwo inverters, the switching arbitrator, at switchover from thesingle-sided drive mode to the dual-sided drive mode, gradually changesand increases, from zero, the power level of the drive-start-sideinverter starting the switching drive from a stopped state, and atswitchover from the dual-sided drive mode to the single-sided drivemode, gradually changes and decreases, to zero, the power level of thedrive-end-side inverter ending the switching drive and shifting to thestopped state.
 2. An electric motor drive device that controls, by usingtwo inverters individually connected to two power sources, driving of amotor including a first winding set and a second winding set of three ormore phases connected by a star connection or a delta connection, theelectric motor drive device comprising: a first inverter that receivesDC power from a first power source, includes a plurality of firstswitching elements so disposed as to correspond to the phases of thefirst winding set, and is connected to the first winding set; a secondinverter that receives DC power from a second power source, includes aplurality of second switching elements so disposed as to correspond tothe phases of the second winding set, and is connected to the secondwinding set; and a control unit comprising: two inverter controlcircuits of a first inverter control circuit that generates a firstvoltage command and a second inverter control circuit that generates asecond voltage command, based on a torque command, the first voltagecommand being an output voltage command to the first inverter, thesecond voltage command being an output voltage command to the secondinverter; and a switching arbitrator that determines switching between asingle-sided drive mode and a dual-sided drive mode and arbitratesoutput of each of the inverters at a time of switching for making outputof the motor continuous before and after the switching between the drivemodes, the single-sided drive mode being a mode in which one of the twoinverters performs switching drive, the dual-sided drive mode being amode in which both the two inverters performs switching drive, wherein,at least one of the inverter control circuits has a function ofadjusting a level of power supplied from the two power sources to thetwo inverters, the switching arbitrator, at switchover from thesingle-sided drive mode to the dual-sided drive mode, gradually changesand increases, from zero, the power level of the drive-start-sideinverter starting the switching drive from a stopped state, and atswitchover from the dual-sided drive mode to the single-sided drivemode, gradually changes and decreases, to zero, the power level of thedrive-end-side inverter ending the switching drive and shifting to thestopped state.
 3. The electric motor drive device according to claim 1,wherein the switching arbitrator determines the switching between thesingle-sided drive mode and the dual-sided drive mode based on at leastone of an output request to the motor, an SOC state of the powersources, or a temperature of the power sources, the inverters, or themotor.
 4. The electric motor drive device according to claim 1, whereinthe switching arbitrator determines the switching between thesingle-sided drive mode and the dual-sided drive mode based on aself-inverter voltage utilization factor calculated by dividing inverterline voltage by inverter input voltage for at least one of theinverters.
 5. The electric motor drive device according to claim 1,wherein, at least one of the inverter control circuits operates as apower management circuit that manages distribution of power suppliedfrom the two power sources to the two inverters, and at the time ofswitching of the drive mode, the switching arbitrator switches a role ofthe power management circuit between the two inverter control circuitsand transfers the last control state to the other side.
 6. The electricmotor drive device according to claim 1, wherein, in a controlconfiguration in which output of the inverters is determined based onvoltage of one of the power sources in the single-sided drive mode, andoutput of the inverters is determined based on a voltage sum of the twopower sources in the dual-sided drive mode, the switching arbitratorinstantaneously corrects a voltage command in response to sudden changein the voltage sum of the two power sources at the time of switching ofthe drive mode, and transfers the voltage command to the next processingcycle.
 7. The electric motor drive device according to claim 1, wherein,in a control configuration in which output of the inverters isdetermined based on voltage of one of the power sources in thesingle-sided drive mode, and output of the inverters is determined basedon a voltage sum of the two power sources in the dual-sided drive mode,the switching arbitrator executes a slow change process for slowlychanging a voltage recognition value on the control with respect to thesudden change in the sum of the two-power source voltages at the time ofswitching of the drive mode.
 8. The electric motor drive deviceaccording to claim 1, wherein, in a case of switchover from thesingle-sided drive mode by one of the inverters as the drive-end-sideinverter to the single-sided drive mode by the other inverter as thedrive-start-side inverter, the drive mode is switched through thedual-sided drive mode, and the switching arbitrator gradually decreasesoutput of the drive-end-side inverter from 100% to 0% and graduallyincreases output of the drive-start-side inverter from 0% to 100% in thedual-sided drive mode.
 9. The electric motor drive device according toclaim 1, wherein, in a case of switchover from the single-sided drivemode by one of the inverters as the drive-end-side inverter to thesingle-sided drive mode by the other inverter as the drive-start-sideinverter, the drive mode is switched through the dual-sided drive mode,and the switching arbitrator transfers a value obtained by multiplyingthe voltage command output from the drive-end-side inverter by acorrection coefficient based on a voltage ratio of the two power sourcesas a voltage command of the drive-start-side inverter.
 10. An electricmotor drive device that controls driving of a motor including openwindings of two or more phases by using two inverters connected to acommon power source, the open windings having end points open to eachother, the electric motor device comprising: a first inverter thatincludes a plurality of first switching elements so disposed as tocorrespond to the phases of the open windings, and is connected to oneends of the open windings; a second inverter that includes a pluralityof second switching elements so disposed as to correspond to the phasesof the open windings, and is connected to other ends of the openwindings; a common high-potential-side wiring that connectshigh-potential-side wirings of the first inverter and the secondinverter; a common low-potential-side wiring that connectslow-potential-side wirings of the first inverter and the secondinverter; a switch that is disposed in at least one of the commonhigh-potential-side wiring and the common low-potential-side wiring andis capable of interrupting a current path; and a control unitcomprising: two inverter control circuits of a first inverter controlcircuit that generates a first voltage command and a second invertercontrol circuit that generates a second voltage command, based on atorque command, the first voltage command being an output voltagecommand to the first inverter, the second voltage command being anoutput voltage command to the second inverter; and a switchingarbitrator that determines switching between a single-sided drive modeand a dual-sided drive mode and arbitrates output of each of theinverters at a time of switching for making output of the motorcontinuous before and after the switching between the drive modes, thesingle-sided drive mode being a mode in which one of the two invertersperforms switching drive, the dual-sided drive mode being a mode inwhich both the two inverters performs switching drive, wherein, in astar connection circuit configured by one inverter establishing neutralpoint coupling, the other inverter is operable in the single-sided drivemode in an open state of the switch, in an H-bridge circuit configuredby the corresponding first switching elements and the correspondingsecond switching elements of the respective phases, operation in thedual-sided drive mode is performed in s closed state of the switch, atleast one of the inverter control circuits has a function of adjusting alevel of power supplied from the common power source to the twoinverters, the switching arbitrator, at switchover from the single-sideddrive mode to the dual-sided drive mode, gradually changes andincreases, from zero, the power level of the drive-start-side inverterstarting the switching drive from a stopped state, and at switchoverfrom the dual-sided drive mode to the single-sided drive mode, graduallychanges and decreases, to zero, the power level of the drive-end-sideinverter ending the switching drive and shifting to the stopped state.11. The electric motor drive device according to claim 10, wherein, in acontrol configuration in which output of the inverters is determinedbased on voltage of the common power source in the single-sided drivemode, and output of the inverters is determined based on a double valueof voltage of the common power source in the dual-sided drive mode, theswitching arbitrator instantaneously corrects a voltage command inresponse to sudden change in the voltage used for determining the outputof the inverters at the time of switching of the drive mode, andtransfers the voltage command to the next processing cycle.
 12. Theelectric motor drive device according to claim 10, wherein, in a controlconfiguration in which output of the inverters is determined based onvoltage of the common power source in the single-sided drive mode, andoutput of the inverters is determined based on a double value of voltageof the common power source in the dual-sided drive mode, the switchingarbitrator executes a slow change process for slowly changing a voltagerecognition value on the control with respect to the sudden change inthe voltage used to determine the output of the inverters at the time ofswitching of the drive mode.
 13. An electric motor drive device thatcontrols, by using two inverters connected to a common power source,driving of a motor including a first winding set and a second windingset of three or more phases connected by a star connection or a deltaconnection, the electric motor drive device comprising: a first inverterthat includes a plurality of first switching elements so disposed as tocorrespond to the phases of the first winding set, and is connected tothe first winding set; a second inverter that includes a plurality ofsecond switching elements so disposed as to correspond to the phases ofthe second winding set, and is connected to the second winding set; acommon high-potential-side wiring that connects high-potential-sidewirings of the first inverter and the second inverter; a commonlow-potential-side wiring that connects low-potential-side wirings ofthe first inverter and the second inverter; a control unit comprising:two inverter control circuits of a first inverter control circuit thatgenerates a first voltage command and a second inverter control circuitthat generates a second voltage command, based on a torque command, thefirst voltage command being an output voltage command to the firstinverter, the second voltage command being an output voltage command tothe second inverter; and a switching arbitrator that determinesswitching between a single-sided drive mode and a dual-sided drive modeand arbitrates output of each of the inverters at a time of switchingfor making output of the motor continuous before and after the switchingbetween the drive modes, the single-sided drive mode being a mode inwhich one of the two inverters performs switching drive, the dual-sideddrive mode being a mode in which both the two inverters performsswitching drive, wherein, at least one of the inverter control circuitshas a function of adjusting a level of power supplied from the commonpower source to the two inverters, the switching arbitrator, atswitchover from the single-sided drive mode to the dual-sided drivemode, gradually changes and increases, from zero, the power level of thedrive-start-side inverter starting the switching drive from a stoppedstate, and at switchover from the dual-sided drive mode to thesingle-sided drive mode, gradually changes and decreases, to zero, thepower level of the drive-end-side inverter ending the switching driveand shifting to the stopped state.
 14. The electric motor drive deviceaccording to claim 10, wherein the switching arbitrator determines theswitching between the single-sided drive mode and the dual-sided drivemode based on at least one of an output request to the motor, an SOCstate of the common power source, or a temperature of the common powersource, the inverters, or the motor.
 15. The electric motor drive deviceaccording to claim 10, wherein the switching arbitrator determines theswitching between the single-sided drive mode and the dual-sided drivemode based on a self-inverter voltage utilization factor calculated bydividing inverter line voltage by inverter input voltage for at leastone of the inverters.
 16. The electric motor drive device according toclaim 10, wherein at least one of the inverter control circuits operatesas a power management circuit that manages distribution of powersupplied from the common power source to the two inverters, and at thetime of switching the drive mode, the switching arbitrator switches arole of the power management circuit between the two inverter controlcircuits and transfers the last control state to the other side.
 17. Theelectric motor drive device according to claim 10, wherein in a case ofswitchover from the single-sided drive mode by one of the inverters asthe drive-end-side inverter to the single-sided drive mode by the otherinverter as the drive-start-side inverter, the drive mode is switchedthrough the dual-sided drive mode, and the switching arbitratorgradually decreases output of the drive-end-side inverter from 100% to0% and gradually increases output of the drive-start-side inverter from0% to 100% in the dual-sided drive mode.